3 min readNew DelhiMay 31, 2026 03:30 PM IST
On Sunday (May 31), an astronomical event known as a “micromoon” will be visible in the night sky, and it will also be a “blue moon”. The National Aeronautics and Space Administration (NASA) stated that just after sunset, a full moon will appear “slightly smaller and dimmer than usual.” This micromoon will be the “farthest, smallest, and dimmest Moon this year,” the space agency added.
Here is what to know about the phenomena, the science behind them, and how you can best spot the moon.
First, what is a blue moon?
Though the expression “once in a blue moon” implies a rare or unusual occurrence, a blue moon is not that rare an astronomical event.
There are a few definitions of a blue moon. One that is most commonly understood — and endorsed by NASA — describes a situation when a full moon is seen twice in a single month. Because the new moon to new moon cycle lasts 29.5 days, a time comes when the full moon occurs at the beginning of a month, and there are days left still for another full cycle to be completed.
Such a month, in which the full moon is seen on the 1st or 2nd, will have a second full moon on the 30th or 31st. According to NASA, this happens every two or three years.
Sometimes, smoke or dust in the air can scatter red wavelengths of light, as a result of which the moon may, in certain places, appear more blue than usual. But this has nothing to do with the name “blue” moon, and the association of the colour with the term is unclear.
And what is a micro moon?
The size of the moon, as perceived from earth, is dependent on its location within its orbit around the earth. The moon’s orbit is an elongated or stretched-out circle and it takes 27.3 days to orbit the earth. According to NASA, the moon is about 363,711 km away at its closest to earth, known as perigee. At apogee, or the furthest point, the moon is about 403,945 km away.
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A smaller-than-usual moon is observable when the Moon’s fully illuminated phase occurs within a short time of apogee. On the other hand, a supermoon occurs when the moon is passing through or is close to its perigee.
Is this a rare event?
When seen in terms of both phenomena happening simultaneously, then yes. “Although the next micromoon occurs next month, and the next blue moon at the end of 2028, the next blue micromoon will not occur until 2053,” NASA stated.
No special equipment is needed to observe this blue micromoon, and it should be clearly visible in the absence of clouds. The BBC’s Sky at Night Magazine suggests the following tips for observing this moon:
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- Head out just before sunset
- Look to the southeast and spot the Blue Moon rise as the sun sets
- Once the sun sets, look to the western sky and see if you can spot bright planets, Venus and Jupiter